<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Title</title>
</head>
<body>
    <table>
      <tr>
        <td class="outer">1001</td>
        <td>tom</td>
        <td>23</td>
      </tr>
    </table>

    <script>
        //即使不写tbody,那么它也是存在的
        //table和tr之间的关系是 '爷孙'
        let td = document.getElementsByClassName("outer")[0];
        let tt = td.parentElement.parentElement;
        console.log(tt) //tbody
    </script>
</body>
</html>